Public Release: 10-Jun-2013
British butterfly desperate for warm weather this summer

IMAGE: The silver-spotted skipper needs temperatures of 25°C to become fully active. When summer weather turns bad the butterfly battles for survival.
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Credit: Zoe Davies

Butterflies are extremely sensitive to changes in temperature and new research has revealed that when summer weather turns bad the silver-spotted skipper battles for survival. The butterfly, which previously faced extinction from habitat loss, is recovering following conservation efforts but the recent cool wet summers in England have almost stalled its progress.

A 27 year study by researchers at the University of Exeter in collaboration with the University of York, the University of Liverpool, Sussex Wildlife Trust, the Centre for Ecology & Hydrology and the charity Butterfly Conservation has been published in the journal Ecology Letters. The study estimated changes in temperature across a range of silver-spotted skipper habitats and found that localised fluctuations in temperature lead to extreme fluctuations in the butterfly population size and in the probability of the butterflies colonising new sites.

Lead author Dr Jonathan Bennie from the University of Exeter said: "Although we know that the climate overall is warming there is still much variability in the weather from one year to the next. This variability presents a threat to southern British butterflies that we might expect to take advantage of warmer conditions to colonise further north. In warmer years the silver-spotted skipper, which needs a balmy 25°C to become fully active, has expanded its range.

However during the recent cold wet summers we have found the skipper clinging to the warmest south-facing hillsides waiting for better weather."
The study used records of weather and butterflies since 1982, combined with computer modelling, to reconstruct how microclimates, created by different slopes and aspects, affect how many butterflies there were, where they were, and how quickly the species has been able to colonise new locations as the climate has warmed.

Co-author Dr Jenny Hodgson from the University of Liverpool said "We were able to produce quite an accurate reconstruction of this butterfly's expansion across the landscape, and this makes us hopeful that we can provide useful predictions of which sites will be most important for conservation in the future."

The research indicates that conservation efforts could benefit from saving habitats with a range of different microclimates. Many species of butterfly are declining in Britain because of habitat loss, but the silver-spotted skipper has taken advantage of south facing slopes with warm microclimates. These provide vital refuges for the species during cooler summers; whereas in hotter summers north, east and west facing hillsides provide stepping stones of habitat that allow the species to spread through the landscape.

Understanding how different species depend on different features of the landscape because of their microclimates would enable more effective conservation of species under a changing and variable climate.

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This work was funded by the Natural Environment Research Council (NERC).

The Sunday Times University of the Year 2012-13, the University of Exeter is a Russell Group university and in the top one percent of institutions globally. It combines world-class research with very high levels of student satisfaction. Exeter has over 18,000 students and is ranked 7th in The Sunday Times University Guide, 10th in the UK in The Times Good University Guide 2012 and 10th in the Guardian University Guide. In the 2008 Research Assessment Exercise (RAE) 90% of the University's research was rated as being at internationally recognised levels and 16 of its 31 subjects are ranked in the top 10, with 27 subjects ranked in the top 20.

The University has three campuses. The Streatham and St Luke's campuses are in Exeter and the Cornwall Campus (known locally as the Tremough Campus) near Penryn. In an arrangement that is unique in the UK, the Cornwall Campus is owned and jointly managed as the Tremough Campus with Falmouth University. At the campus, University of Exeter students can study programmes in the following areas: Animal Behaviour, Conservation Biology and Ecology, English, Environmental Sciences, Evolutionary Biology, Geography, Geology, History, Mathematics and the Environment, Mining and Minerals Engineering, Politics and International Studies, Renewable Energy and Zoology.

The University has invested strategically to deliver more than £350 million worth of new facilities across its campuses for 2012, including landmark new student services centres - the Forum in Exeter and The Exchange in Cornwall - and world-class new facilities for Biosciences, the Business School and the Environment and Sustainability Institute.

The Natural Environment Research Council (NERC) is the UK's main agency for funding and managing world-class research, training and knowledge exchange in the environmental sciences. It coordinates some of the world's most exciting research projects, tackling major issues such as climate change, food security, environmental influences on human health, the genetic make-up of life on earth, and much more. NERC receives around £300m a year from the government's science budget, which it uses to fund research and training in universities and its own research centres.

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